Reflection barrier for panoramic display

ABSTRACT

A panoramic display system includes a curved projection screen, a panoramic projector, and a substantially conically shaped barrier. The projector is configured to project an image onto the projection screen from a projection point located substantially above the projection screen. The conical barrier has a base disposed toward the bottom of the projection screen, and an apex region disposed toward the projection point. The barrier blocks scattered light from reflecting from portions of the curved screen to other portions thereof.

The present application is a continuation-in-part of copending U.S.patent application Ser. No. 10/642,880 filed on Aug. 18, 2003 andentitled WIDE ANGLE SCANNER FOR PANORAMIC DISPLAY.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to panoramic visual displaysystems. More particularly, the present invention relates to a barrierfor reducing light scattering on a panoramic display screen.

2. Related Art

A panoramic display is generally considered one in which the horizontaldimension is much greater than the vertical dimension, such that thedisplay horizontally wraps around the viewing point, at least partially.Panoramic visual display systems are desirable in a number ofapplications. One particular application needing wide fields of view isflight simulation and training. Heretofore, panoramic flight simulatorvisual display systems have typically used multiple projectors, withtheir separate images edge-blended in a mosaic to create an apparentlycontinuous wide field of view. Anywhere from three to ten or moreindividual projectors are commonly used, and multiple projector displayswith 64 or more separate projectors have been proposed to meet the needfor high resolution imagery over a very wide field of view.

Two types of such displays have frequently been used in simulation andtraining. The first type, shown in FIG. 13, comprises a panoramic realimage display system 100, wherein a projected real image 102 is viewedby an observer from a viewing point 106 near the center of a curvedfront projection screen 108, in this case a dome. In such a system,multiple projectors 110 are typically located above and/or behind theviewer, preferably outside of view. For very large fields of view, anearly complete dome display screen is used, as shown. However, itbecomes increasingly difficult with increasing field of view to placeprojectors in locations that provide uniform illumination andresolution, yet are still hidden from view. In addition, current methodsfor blending the edges of images from adjacent projectors are notcompletely effective at hiding the seams between images, and colormatching of adjacent images from multiple projectors is very difficult.The common result is composite images with noticeable seams andinconsistent coloring from one portion of the image to another.

Another frequently used display type is a wide angle virtual display112, shown in FIGS. 14 and 15. This type of display is frequently usedfor civil aviation simulators. In this type of display, an observerviews a concave mirror 114 which provides a reflection of an image thathas been projected onto a back-projection screen 116. The object for thecollimating mirror is a real image projected by multiple projectors 118.In this system both the projectors and the eyepoint 120 (inside thesimulator cockpit 122) are offset from the center of curvature 126 ofthe screen, and the center of curvature 124 of the mirror.

The geometry shown in FIGS. 14 and 15 creates problems for projectors ingeneral and for panoramic displays with multiple projectors inparticular. As illustrated in FIG. 15, there is a single point 130 inspace that is preferred by an optical projection system for directingthe greatest amount of light toward the viewing location 120. Ideally,all of the light would be projected downward and around from this pointto all areas of the projection screen 116. However, it is impossible tolocate multiple projectors at a single point in space. Additionally, thelow f-number lenses required for CRT projectors normally used do nothave sufficient depth of focus to allow positioning at the preferredlocation 130. Also, large projectors in these positions are problematicfor training applications that use motion bases. The large mass ofmultiple projectors placed high above the screen creates an unacceptablylarge moment of inertia for simulators or other applicationsincorporating motion systems. For these reasons, current wide-anglevirtual systems, such as that shown in FIG. 14, have projectors locatedin a compromised position below and behind the ideal location.

A laser projector can have sufficient depth of focus to project from theideal point well above the screen, but it must be scanned with asignificant downward tilt relative to the vertical axis of the screen.The type of scanner that has been used with laser projectors in the pastis not capable of the wide angle, tilted scan required for both a wideangle virtual display and a panoramic real image display.

Panoramic scanners have been developed for linear detector arrays. Inprior systems, wide angle scanning of a linear (or two dimensional)array of sensors or light modulators is usually done with a mirror orprism at a 45 degree angle to an axis of rotation that is perpendicularto the axis (or plane) of the sensor. Since such an arrangement causesthe projected or sensed image to roll through 360 degrees for eachrevolution of the scanning element as it is rotated, such scannersnormally incorporate a doubly reflecting mirror system or prism rotatingat half the scanner rate to restore the image to the proper orientation.These systems provide a full 360 degree scan, but require an imagederotator turning continuously at one half the scan rate. Since suchsystems require dynamic synchronization of two elements rotating atdifferent rates while maintaining precise optical alignment throughmultiple reflections, they are expensive to produce, suffer fromaccuracy problems, and are heavy and difficult to balance. Consequently,they are seldom used for high speed scanning systems.

In the past, laser projectors have only had the capability to scan asingle beam of light over a narrow angle while modulating it one pixelat a time to create a projected raster. There are many types of laserprojectors that scan a single beam in a raster fashion, such as using arotating polygon wheel for a fast axis, and a galvanometer for a slowaxis. This type of projector is limited in image size vs. projectiondistance, and therefore creates a narrow image. These types ofprojectors sometimes use a magnifying lens to shorten the throwdistance. This method is unsuitable for a panoramic display because itmagnifies the pixels in both the horizontal and vertical directions.Additionally, bandwidth limitations have hindered the development of ahigh resolution panoramic display from a single projector modulating asingle laser beam.

One method of scanning a linear array to form an image uses a gratinglight valve (GLV) to project a linear array over a narrow field of viewon a flat screen. Unfortunately, mere use of a GLV does not address theproblem of creating a panoramic display on a curved screen. Priorsystems for wide angle image projection also include head-mounted laserprojectors incorporating a line scanner. This type of system scans a1-dimensional image over a relatively limited field of view. Since thereis no offset, the scanner must be mounted at the viewing position (e.g.on a helmet).

One problem frequently encountered with panoramic display systems,whether real or virtual, is light scattering. As shown in FIG. 1, someportion of the light that strikes one area of a curved screen 14 tendsto scatter and reflect toward other parts of the screen, as indicated byarrows 198. This scattered light tends to wash out the image, and reducethe contrast of the display. Obviously, this adversely affects thequality of the image.

SUMMARY OF THE INVENTION

It has been recognized that it would be advantageous to develop a directview display system that can project a wide field of view from a singleprojection location that is more nearly optimized for a uniform display,and provides good color matching and no seams.

It has also been recognized that it would be advantageous to develop asystem and method for reducing light scattering with a panoramic displaysystem.

The invention advantageously provides a wide angle display systemincluding a linear array projector, a curved display surface, and asubstantially planar scanning mirror. The linear array projector isconfigured to project an image along an optical axis toward the scanningmirror. The scanning mirror is configured to continuously rotate aboutan axis substantially in the plane of the mirror, and to reflect theimage onto the display surface.

In accordance with another more detailed aspect of the presentinvention, the scanning mirror includes two parallel, opposingreflective sides, and rotates at one half the refresh rate of theprojector.

In accordance with yet another more detailed aspect of the presentinvention, the linear array projector is configured to project an imagecomprising a series of lines of pixels, and the rotational axis of thescanning mirror is parallel to the lines of pixels. The scanning mirroris configured to reflect the lines of pixels onto and scan the imageacross the curved display surface.

In accordance with another embodiment of the invention, the system cancomprise multiple linear array projectors projecting images at thescanning mirror, so as to produce a composite panoramic image on thedisplay surface.

In accordance with still another more detailed aspect of the presentinvention, the system can comprise a polygonal scanning mirror with aplurality of vertical reflective faces, configured to reflect imagesfrom a plurality of linear array projectors.

In accordance with another aspect thereof, the invention advantageouslyprovides a panoramic display system, comprising a curved projectionscreen, having a center of curvature and a bottom, a panoramicprojector, configured to project an image onto the projection screenfrom a projection point located substantially above the projectionscreen, and a substantially conically shaped barrier, having a basedisposed toward the bottom of the projection screen, and an apex regiondisposed toward the projection point. The barrier blocks scattered lightfrom reflecting from portions of the screen to other portions thereof.

Additional features and advantages of the invention will be apparentfrom the detailed description which follows, taken in conjunction withthe accompanying drawings, which together illustrate, by way of example,features of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of a wide angle scannerin accordance with the present invention.

FIG. 2 is an elevational view of the wide angle scanner of FIG. 1.

FIG. 3 is a perspective view of a wide angle virtual display flightsimulator incorporating an alternative embodiment of wide angle scannerin accordance with the present invention.

FIG. 4 is an elevational view of a wide angle real image displayincorporating a wide angle scanner similar to that of FIG. 3.

FIG. 5 is a top view of the wide angle scanner of FIG. 4.

FIGS. 6 a-6 d are top views of a planar scanning mirror and foldingmirror, showing the relative effects of articulation of the foldingmirror.

FIG. 7 is a top exaggerated view of a planar scanning mirror and curvedscreen, showing some effects of the mirror thickness relative to theposition of projection on the display screen.

FIG. 8 is an exaggerated side view of a planar scanning mirror, showingsome effects of the mirror thickness relative to apparent pixel size.

FIG. 9 is a diagram showing the effects of deviation of the pixel linefrom the vertical.

FIG. 10 is a plan view of a panoramic scanner system incorporating twoprojectors and a planar scanning mirror to produce a 360° image.

FIG. 11 is a plan view of a panoramic scanner system incorporating threeprojectors and a polygonal scanning mirror to produce a panoramicdisplay.

FIG. 12 is an elevational view of a panoramic scanner systemincorporating multiple projectors in a single unit, with a foldingmirror for each projector, and a single polygonal scanning mirror.

FIG. 13 is a pictorial view of a prior art flight simulator employing areal image display using multiple projectors for producing a panoramicimage on the inside of a dome display surface.

FIG. 14 is a pictorial view of a prior art flight simulator employingmultiple projectors for producing a panoramic virtual image.

FIG. 15 is an elevational view of the flight simulator of FIG. 14.

FIG. 16 is a perspective view of a panoramic projection systemincorporating a reflection barrier according to the present invention.

FIG. 17 is a perspective view of a panoramic virtual projection systemincorporating a reflection barrier according to the present invention.

FIG. 18 is a perspective view of a panoramic projection system havingmultiple projectors aimed at a single scanning mirror and incorporatinga reflection barrier according to the present invention.

FIG. 19 is a perspective view of a panoramic screen and truncatedreflection barrier having baffles for blocking scatter and reflectionsaround the back of the reflection barrier.

DETAILED DESCRIPTION

Reference will now be made to the exemplary embodiments illustrated inthe drawings, and specific language will be used herein to describe thesame. It will nevertheless be understood that no limitation of the scopeof the invention is thereby intended. Alterations and furthermodifications of the inventive features illustrated herein, andadditional applications of the principles of the inventions asillustrated herein, which would occur to one skilled in the relevant artand having possession of this disclosure, are to be considered withinthe scope of the invention.

The inventors have developed a new type of laser scanner for surroundinga viewer with a panoramic image. For purposes of this discussion, theterms “panoramic image” and “panoramic display” are used to refer to adisplay or image in which the horizontal dimension is much greater thanthe vertical dimension. It will be apparent that “horizontal” and“vertical” are relative terms. They do not refer to any particularrelationship to the earth's horizon, but refer to arbitrary orthogonalaxes. The importance of the vertical relative to the horizontal willbecome more apparent from the discussion below.

For direct view display systems, it is desirable to project a wide fieldof view from a common location, which is more nearly optimized for auniform display and provides good color uniformity, without seams. For asystem like that shown in FIG. 13, the preferred projector location tomeet these requirements would be somewhere near the center of the dome,but behind and above the viewing point 106. A similar system would bedesirable for wide angle virtual systems, such as that shown in FIGS. 14and 15, where the viewing point 120 is offset from the optical axis of ascreen and mirror.

The present invention addresses these issues by projecting a verticalcolumn of pixels created by a linear array spatial light modulator asthe image source. This column of pixels is scanned across a wide angleto create a panoramic field of view, with the scanner located above andbehind the viewing point. This offset geometry creates problems forprojectors in general and for panoramic displays using multipleprojectors in particular. In general, projectors should be located closeto the viewing point for best brightness and contrast. This becomesdifficult when multiple projectors are used, as shown in FIGS. 13 and14. The wide angle laser scanner of the present invention addressesthese problems.

FIGS. 1 and 2 show one embodiment of a panoramic real image displaysystem 10 which the inventors have built in accordance with the presentinvention. This system comprises a linear array projector 12 (i.e. GLVprojector), a curved display screen 14, and a flat (i.e. substantiallyplanar) scanning mirror 16 having a rotational axis 18 in the plane ofthe mirror. The curved display screen has an axis or center of curvature20. The rotational axis is parallel to and preferably collinear with theaxis of curvature.

The primary viewer location or eyepoint 22 is located below the scanningmirror 16 and approximately on the rotational axis/axis of curvature18/20, viewing the concave side of the screen 14. However, the displayscreen could be a back projection screen, thus creating a secondaryviewer location 24 viewing the convex side of the curved screen. Whilethe screen shown in FIGS. 1 and 2 is curved about a single axis (i.e.the screen forming a portion of a cylinder), this embodiment of theinvention could also be used with a double-curved screen (i.e. thescreen forming a portion of a sphere), as is depicted in FIGS. 3 and 4.

The linear array projector 12 projects an image along an optical axis 26toward the scanning mirror 16, which reflects the image onto the screen14. The optical axis is oblique to the rotational axis 18 of thescanning mirror. In order to scan a projected field that wraps aroundthe eyepoint 22, the direction of projection must be at an oblique angleto the axis of rotation of the scanner. This is necessary in order forthe light from the scanning mirror not to reflect back onto theprojector as it scans through a continuous field of view. Otherwise, thebody of the projector itself would cast a shadow on a portion of thescreen. This also allows the scanner to be located at a position otherthan at the eyepoint of the panoramic real image display.

Advantageously, the invention does this without a separate derotatingelement. Instead, it scans a linear array over a panoramic field of viewwithout a second derotating element turning at a different velocity fromthe scan. The projector is configured to produce the image bycontinuously scanning a vertical (rather than horizontal) line of pixels28. The designation of “vertical” is relative to the orientation of therotational axis 18 of the scanning mirror, which corresponds to thevertical dimension of the panoramic image, discussed above. Theprojected line of pixels is parallel to the rotational axis of thescanning mirror.

The scanning mirror 16 is configured to continuously rotate about itsrotational axis 18 to reflect the image onto the screen 14. The imageproduced by the GLV projector 12 is continuously scanned at a refreshrate, such as 60 Hz. During each refresh cycle, the planar scanningmirror rotates through one half of a rotation, reflecting each scannedvertical line 28 of the image onto the screen at its proper location toreproduce the total image. The angular swing of the mirror causes theimage to be projected across a very wide arc, resulting in a widepanoramic image. In one embodiment, the scanning mirror has tworeflective sides, 16 a, 16 b, and rotates at a rate that is half therefresh rate (i.e. 30 Hz). This is possible because each side of themirror scans the image across the screen during one refresh cycle of theprojector, and then faces away during the next cycle.

The projector 12 has a projection lens 30 with an external pupil 32 toproject the image of the vertical column of pixels 28. It will beassumed for the purpose of this discussion that the real image at thispoint consists of the vertical column of pixels that can be modulated asthe scanner rotates to form a two-dimensional image on the screen 14.The scanning mirror 16 is preferably located at the position of theexternal pupil 32. This is done so that the image produced on thescanning mirror will be as small as possible, thus allowing use of asmaller mirror. The projection lens is oriented to produce an angle φbetween the optical axis 26 and the axis of rotation 18 of the scanningmirror. The angle φ is chosen to achieve the proper offset of theprojection point (i.e. location of the projector lens) versus theviewing point 22 for a real image display system. An angle of φ =55degrees has been used in this system, though other angles could also beused.

The scanning mirror 16 is the main scanning mechanism, drivencontinuously by a servomotor (not shown) which is phase-locked to theimage update rate of the projector 12, typically 60 Hz. In one example,approximately 110 degrees of the continuous 360 degree rotation of thescanning mirror assembly is used for each side of the mirror assembly tocreate two continuous 220 degree scans relative to the eyepoint 22 onthe viewing screen 14 for each rotation of the mirror. This requires a30 Hz (1800 RPM) rotation rate of the scanning mirror.

The rotating scanning mirror 16 presents certain technicalconsiderations because of its rotation and because of its geometry. Someof these are illustrated in FIGS. 7-9. One consideration is therotational motion of the mirror. As shown in FIG. 9, the obliqueincidence of the projected image (line of pixels) 28 on the rotatingmirror would normally cause the projected image to rotate, indicated bythe dashed line 34. However, since the image formed by the GLV isessentially a vertical column of pixels of zero thickness, no imagerotation occurs as long as the line of pixels is parallel to the axis ofrotation 18 of the scanning mirror, and there is no component of theline image which is perpendicular to the axis of rotation of thescanning mirror.

Another consideration is the thickness of the mirror. As noted, thescanning mirror assembly 16 utilizes a two sided mirror. Since themirror cannot have zero thickness, each scanning mirror surface has asmall offset T (equal to half the total thickness of the mirror) fromthe axis of rotation 18, as shown in FIGS. 7 and 8. This offset causesthe image to be slightly deflected both in the horizontal and in thevertical direction as the scanning mirror rotates. As shown in FIG. 7,if each mirror surface 16 a, 16 b of the scanning mirror is offset adistance T from the axis of rotation, the image source will interceptthe mirror a distance ΔT closer as the mirror rotates from the normalposition. As seen from the side view of FIG. 8, this will cause theimage to be displaced in distance ΔP upwards on the screen to the leftand right of the horizontal center of the screen. The inventors havecalculated the magnitude of ΔP for various conditions, and have foundthat it is well within the error budget for both collimated and directview display applications.

The mirror offset from the axis of rotation also causes a horizontaldisplacement of the image with rotation. As shown in FIG. 7, the imagesource intercepts the mirror surface 16 a, 16 b at a distance T from theaxis of rotation and as the mirror rotates this distance is increased byΔT. The inventors have found that the angular error E is less than 0.7degrees for a mirror of 0.5″ thickness and a screen having a 48″ radius.This level of error is considered acceptable for most applications. Bothhorizontal and vertical errors can be set to zero in the forward fieldof view, and increasing to the values indicated at +/90 degrees ofazimuth. If greater geometric accuracy is required, it can be obtainedby performing Non-Linear Image Mapping (NLIM) in the image generator.

The oblique angle of incidence onto the projection screen also causes atop to bottom defocus of the image. Those skilled in the art willrecognize that this can be corrected by a scheimpflug tilt of the GLV.Geometric correction for the image keystone and projection onto aspherical screen can also be performed by NLIM in the image generator.

Additional embodiments of wide angle displays in accordance with theinvention are depicted in FIGS. 3-5. A wide angle virtual display 50(similar to the configuration of FIG. 14) is shown in FIG. 3. A wideangle real image display 60 using the same type of projection system isdepicted in FIG. 4, with FIG. 5 providing a plan view of this system.This embodiment of the projection system provides a panoramic displayemploying two mirrors, rather than just one. In this embodiment, the GLVprojector 52 and projection lens 54 are essentially the same as in theembodiment of FIG. 1. The projector directs an image along an opticalaxis 55 toward a flat folding mirror 56. The folding mirror 56 reflectsthe image to the scanning mirror 58, which reflects the image to thecurved projection screen 62. As with the embodiment of FIGS. 1 and 2,the projection lens 54 of the projector has an external pupil 76, andthe scanning mirror 58 is preferably placed at the position of theexternal pupil so that the size of the projected rays on the mirror willbe as small as possible. An external pupil is preferred, but lenses withan internal pupil can also be used, and simply require a larger mirror.

The scanning mirror 58 is located with its rotational axis 64 parallelto and preferably collinear with a vertical axis 66 (i.e. axis ofcurvature) of the curved projection screen 62. It will be apparent thata double-curved surface, such as the screen shown in FIG. 3, has aninfinite number of axes of curvature. However, there is one preferredaxis of curvature that is the axis of horizontal curvature with respectto the orientation of the panoramic image. In other words, an axis thatis parallel to the vertical dimension of the image and represents thecenter of horizontal curvature of the screen is the desired axis ofcurvature.

The scanning mirror has two parallel reflective sides 58 a, 58 b, thatare opposite each other and symmetrical about the axis of rotation. Thescanning mirror rotates continuously in the direction of arrow 68 toscan a regularly updated image onto the screen. The rotational axis ofthe scanning mirror is parallel to and located a distance A from thevertical axis 70 of the folding mirror. The distance Δand the height ofboth mirrors are chosen to ensure that all projected rays are acceptedby the scanning mirror and clear the folding mirror upon reflection fromthe scanning mirror. The resulting image can either be viewed directlyfrom a primary viewpoint 72 below the scanning mirror, or a secondaryviewpoint 72 a outside the curvature of the screen (when using aback-projection screen). Alternatively, as depicted in FIG. 4, the imagecan be viewed via a reflection from a large collimating mirror 74 placedforward of a rear projection screen, as shown in FIG. 3, and followingthe geometry shown in FIG. 15. The embodiment of FIG. 3 essentiallyreplaces the multiple projectors 110 of FIGS. 14 and 15 with a singleprojector and scanning mirror at or near the same location or a betterlocation, so as to provide the same panoramic image.

As with the embodiment of FIG. 1, the optical axis 55 is at a downwardtilt angle φ, this angle being selected so as to place the projector ata better location for either the real image display or the collimatedwide angle virtual display. The optical axis is oblique to the axis ofthe scanning mirror so that the scanner can be located at a positionother than at the eyepoint or primary viewer location 72 of thepanoramic real image display of FIG. 4, and to allow the main lobe oflight from a back projection screen to be directed largely toward theeyepoint in the virtual display of FIG. 3. In the embodiments depictedin FIGS. 3-5, the display screens 62 are depicted as beingdoubly-curved. However, the display system of these embodiments couldalso be used with a singly-curved display surface, as in the embodimentof FIG. 1. Likewise, the screens could be front- or back-projectionsscreens in the real image displays of FIGS. 1, 2, 4, and 5.

The folding mirror 56 is normally fixed, but can be articulated oroscillated about its vertical axis 70 for a wider field of view, asillustrated in FIGS. 6 a-6 d. It is understood that a single mirrordoubles the incident angle of light upon reflection. When two mirrorsare articulated in series, an additional scanning increment is achieved,which may be required for some very wide field-of-view applications.Viewing the top-down views of the folding mirror 56 and scanning mirror58 in FIGS. 6 a-6 d, the light bundle 80 reflected off the mirrorsconverges to a line on the screen 62, but has significant cross sectionat the mirrors. For small projection angles, all of the light can becollected and reflected by the scanning mirror, as shown in FIG. 6 a.For larger angles, the edge 82 of the scanning mirror will begin toblock some of the light as shown in FIG. 6 b. However, if the foldingmirror is rotated slightly relative to the scanning mirror, as shown inFIG. 6 c, then all of the light can be directed toward the screen for awider projection angle.

As the scanning mirror 58 rotates through a single scan cycle (i.e. onehalf rotation), the folding mirror 56 rotates slightly in the oppositedirection, following the motion of the scanning mirror. This allows theentire light bundle 80 of the image to strike the mirror at the extremebeginning of the cycle, as shown in FIG. 6 c, and at the extreme end ofthe cycle, as shown in FIG. 6 d. When the scanning mirror reaches theend of a single scan cycle, the folding mirror must rapidly revert backto its position at the beginning of the scan cycle, and repeat theprocess. This arrangement requires the folding mirror to rapidlyoscillate between the positions shown in FIGS. 6 c and 6 d at a ratethat is twice the rotational frequency of the scanning mirror. Thisoscillation is indicated by the two headed arrow 84 in FIGS. 3 and 5. Itwill be apparent that the rotational axis 70 of the folding mirror isparallel to the rotational axis 64 of the scanning mirror, so that norotation of the image is produced by the oscillation of the foldingmirror. This configuration advantageously allows the system to produce awider field of projection. The inventors have found that with thisconfiguration a panoramic image 270° wide can be produced using a singleprojector.

Advantageously, the wide angle display system of the present inventioncan be configured with multiple projectors, which can allow a full 360°scan, and/or accommodate projectors or systems with various limitations.For example, as shown in FIG. 10, a multiple projector system 90 can beprovided with two projectors 92 oriented on opposite sides of a singletwo-sided planar scanning mirror 94. As the mirror rotates, the verticalline of pixels from each projector is scanned across one half of thefull circle screen 96 to give a fully-surrounding panoramic image. Oneprojector 92 a will project an image 98 a across a first half of thescreen, from point A to point B, while the other projector scans animage 98 b across a second half of the screen from point B to point A.As with the prior systems described above, this system can be used withsingle- or double-curved, front- or rear-projection screens.

The configuration of FIG. 10 is not limited to two projectors, but canbe used with any number of projectors. For example, additionalprojectors 98 c, 98 d, can be located so as to further subdivide theportion of the image provided by a single projector. The incorporationof additional projectors can be desirable to increase the resolution ofthe total image. For example, where each projector provides a maximumpixel density in the horizontal dimension, the pixel density of thetotal composite image can be increased by using multiple projectors.This technique can be used even if a full-surround image is not desired.For example, with the embodiment of FIG. 1, two projectors could beaimed at the same scanning mirror, each projector offset some angulardistance from the other, and each providing half of the panoramic image,though not creating a composite image that fully surrounds theviewpoint.

Multiple projectors can also be used to overcome bandwidth limitationsin the image generator (IG). If one IG channel only has the capacity toscan a relatively narrow or lower resolution image at the desiredrefresh rate, multiple IG channels can be used to provide the desiredhigh-resolution image as a composite of images from several projectors.

Another embodiment of a panoramic projection system 140 employingmultiple projectors is shown in FIG. 11. This configuration uses apolygonal scanning mirror 142 to scan the image across the circularscreen 144. As shown, the scanning mirror is a triangular shape, havingthree vertical reflective sides 146. Other shapes can also be used. Asthe mirror rotates about its vertical axis 148 through a full circle, itsequentially reflects the image from each projector 150 a-150 c onto aportion of the screen.

The embodiments of FIGS. 10 and 11 each comprise multiple projectors anda single scanning mirror. However, the advantages of a folding mirrorcan also be incorporated into a multiple projector system. Referring toFIG. 12, a multi-projector panoramic display system 160 includes aplurality of folding mirrors 162 that are oriented to reflect imagesfrom multiple projectors 164 to a single scanning mirror 166. In theexample shown, the scanning mirror is a four-sided polygon, and themultiple projectors are disposed in a single housing 168 locateddirectly above the scanning mirror. This configuration allows therelatively bulky projectors to be located in a less conspicuouslocation, yet still scan the image onto the panoramic screen 170.

The invention provides the advantages of wide angle scanning from anoffset projector position. The system advantageously allows projectionof an image across a circular arc of more than 180 degrees using asingle projection source. As noted above, the various embodiments of thepanoramic scanner can be used for both real image and virtual projectionsystems, using either a front- or back-projection screen that is eithersingly or doubly curved. The invention can be used for wide anglevirtual displays for both civil and military training, and for directview panoramic displays for deployable military trainers. It may alsohave application for command/control type displays, or displays forremote control of unmanned air or ground vehicles. The invention may beadapted for helmet-mounted displays as well. Many other uses are alsopossible. For example, real-image rear-projection panoramic displays canbe used for advertising or informational kiosks at trade shows, in ashopping mall, an airport, or a museum. A composite real-time image ofthe earth from weather satellites could be projected onto the inside ofa spherical back-projection screen, and viewed from outside to provide acomplete perspective of global weather and geography. Advantageously,with the present invention, horizontal magnification is achieved bymechanical rotation of a very simple and aberration-free optical element(a flat mirror), without the need for an exotic and expensive anamorphicprojection lens. The invention also scans over a large field of view,while being mounted away from the viewer location, unlike somehead-mounted laser projectors. Also, unlike some other panoramicscanning systems, the present system does not require a second rotatingelement to act as a derotator.

As noted above, one problem frequently encountered with panoramicdisplay systems, whether real or virtual, is light scattering. Thepresent invention advantageously provides a reflection barrier forpanoramic projection systems that reduces light scattering from one partof a panoramic screen to another, thereby reducing the negative effectlight scattering and reflections have on the contrast of the image onthe screen. Advantageously, it can be employed with mosaic images frommultiple projectors, or with single panoramic images projected from asingle linear array projector and scanned using a rotating scanningmirror. The system provides benefits when using both single- anddouble-curved screens, and can be used with front- and rear-projectionscreens, though it is particularly suited to rear-projection systems.

As shown in FIG. 1, some portion of the light that strikes one area of acurved screen 14 tends to scatter and reflect toward other parts of thescreen, as indicated by arrows 198. This problem exists whether theprojection is from one or more projectors, or using a scanning mirrorsystem disclosed above. This scattered light tends to wash out theimage, and reduce the contrast of the display. Obviously, this adverselyaffects the quality of the image.

Advantageously, the inventors have developed a reflection barrier forpanoramic displays that reduces the effects of light scattering on apanoramic screen. Referring to FIG. 16, the invention is shown inconnection with a panoramic scanning system like that shown in FIG. 1.The panoramic display system 10′ includes a curved projection screen14′, having a bottom 200 and a center of curvature or central axis 18′.The screen is preferably a rear projection screen, directly viewablefrom a viewer location 24′ outside the screen, and may be singly ordoubly curved. As shown in FIG. 17, the system may alternativelycomprise a virtual display system 50′, including a curved mirror 74′,configured to reflect a panoramic image from a rear-projection screen62′ to an offset viewing point 202, such as within in a simulatorcockpit 204.

The system of FIG. 16 includes a panoramic projection system that isconfigured to project an image onto the projection screen 14′ from aprojection point 206 located substantially above the projection screen.It will be apparent that the terms “above”, as well as the designationof the “bottom 200” of the screen and other such terms as used hereinare relative to the panoramic orientation of the projection system andthe screen, and do not necessarily have any relation to any absoluteorientation. It will be apparent that the orientation of the systemcould be inverted from that shown, or disposed in any other position solong as the relative location of the components of the system is asdescribed herein. Thus, the term “above” as used herein could actuallymean “below” or “to the side of.” Regardless of the orientation of thesystem, the projection point is offset from the screen toward a sideopposite to the edge of the panoramic display called the “bottom” inthis description.

The projection system of FIG. 16 may comprise multiple projectors (notshown) disposed near the projection point, configured to project acomposite image upon the screen, similar to the prior art multipleprojector systems described above, such as that depicted in FIG. 13.Alternatively, and more preferably, the projection system comprises alinear array projector 12′, configured to project a vertical line ofpixels 28′ onto the screen 14′ at a refresh rate. The embodiment of FIG.16 is similar to that of FIG. 1, and includes a rotating scanning mirror16′ disposed substantially at the projection point 206, and configuredto rotate about a vertical axis 20′ at one half the refresh rate of thelinear array projector. The scanning mirror reflects the vertical lineof pixels onto the screen at the refresh rate to produce the panoramicimage.

As shown in FIG. 17, the projection system may further comprise afolding mirror 56′, disposed between the linear array projector 52′ andthe scanning mirror 58′. As with the embodiments described above, thefolding mirror is configured to reflect the vertical line of pixels ontothe scanning mirror. The folding mirror allows a different offsetlocation for the projector, and, where the folding mirror oscillatesabout a vertical axis 208, it can also allow a wider panoramic image tobe produced from a single projector.

The panoramic screen 14′ includes a vertical axis of curvature 18′ thatis parallel to and preferably collinear with the rotational axis 20′ ofthe scanning mirror 16′. Disposed within the central space surrounded bythe screen is a substantially conically shaped reflection barrier 210that is oriented upright, with its apex region 212 disposed toward theprojection point 206, and its base 214 toward the bottom or base 200 ofthe screen. Because of its location and its shape, the reflectionbarrier does not interfere with the projection onto the screen, butadvantageously blocks a substantial portion of scattered light fromreflecting from one part of the screen to other parts thereof, asindicated by arrows 215.

The conical barrier 210 is slightly truncated, as shown, with itstheoretical apex 216 located at or near the center of the scanningmirror 16′, but being truncated to provide space for the scanning mirrorand its associated structure. This allows the conical surface 218 of thebarrier to be substantially parallel to the bottom of the projectionpath of the image, yet without interfering with the projection of theimage or the operation of the scanning mirror. The base 214 of thebarrier may be coterminous with the bottom 200 of the screen 14′, or maybe disposed some distance from it. It will be apparent that it isdesirable to locate the surface of the barrier as close to theprojection path of the image as possible so as to block as muchscattered light as possible.

In one embodiment, the reflection barrier 210 has a vertical axis 220that is substantially parallel to the vertical axis of curvature 18′ ofthe screen 14′. More particularly, the vertical axis of the conicallyshaped barrier may be collinear with the vertical axis of the screen.The projection point 206 need not be above the level of the top edge 222of the screen. However, it will be apparent that, where the cone istaller, it will be able to block a greater portion of scattered lightfrom striking other portions of the screen. However, keystonedistortions and other considerations, such as increased moment ofinertia for motion systems, also work to limit the height of the conicalbarrier. The reflection barrier may also be treated to further reduceits reflectivity, such as with the application of an anti-reflectivecoating, baffles, or optical felt disposed on its surface 218.

Because the reflection barrier 210 occupies the space in the interior ofthe screen 14′, it will be apparent that it would be difficult to view afront-projection screen using this invention. A truncated reflectionbarrier could be disposed above an interior viewer location for afront-projection screen, but such a barrier would only improve contrastat the top of the screen. Consequently, the invention is preferably usedwith rear-projection real image systems, with a viewer location 24′outside the screen, as shown in FIG. 16, or with virtual image systems,as in FIG. 17, where the viewer location 202 is located relative to acurved mirror 74′ that provides a reflection of an image from arear-projection screen 62′.

A reflection barrier can be used with a multiple projector system 90′,as shown in FIG. 18. This system includes a 360° panoramic screen 96′and a pair of projectors 92 a′, 92 b′ oriented on opposite sides of andaimed at a common rotating scanning mirror 94′. As the mirror rotates,the vertical line of pixels from each projector is scanned across onehalf of the full circle screen 96′ to give a fully-surrounding panoramicimage. One projector 92 a′ will project an image across a first half ofthe screen, from point A to point B, while the other projector 92 b′scans an image across a second half of the screen from point B to pointA.

As with the prior systems described above, this system can be used withsingle- or double-curved, front- or rear-projection screens. Where thepanoramic screen is not a fill-surround (i.e. not 360°), as in FIG. 17,it will be apparent that the conical reflection barrier 210′ need not becompletely round, but may have a vertically truncated rear side 224.Where the screen defines an arc of more than 180° but less than 360°, asshown in FIG. 19, it will be apparent that scattering and reflectionsare possible between opposing portions near the back edge 226 of thescreen. To prevent this, baffles 228 are provided to enclose the spacebetween the back edge of the screen 14′ and the surface of thereflection barrier 210′.

Where a full-surround screen is used, as in FIG. 18, a completelycircular conical barrier is desirable. Such a system could be configuredwith any number of projectors, and could use a flat or polygonalscanning mirror, as discussed above. Likewise, such a system could beconfigured with one or more folding mirrors, as discussed above.

It is to be understood that the above-referenced arrangements areillustrative of the application for the principles of the presentinvention. Numerous modifications and alternative arrangements can bedevised without departing from the spirit and scope of the presentinvention while the present invention has been shown in the drawings anddescribed above in connection with the exemplary embodiments(s) of theinvention. It will be apparent to those of ordinary skill in the artthat numerous modifications can be made without departing from theprinciples and concepts of the invention as set forth in the claims.

1. A panoramic display system, comprising: a) a curved projectionscreen, having a center of curvature and a bottom; b) a panoramicprojector, configured to project an image onto the projection screenfrom a projection point located substantially above the projectionscreen; and c) a substantially conically shaped barrier, having a basedisposed toward the bottom of the projection screen, and an apex regiondisposed toward the projection point, configured to block reflectionsfrom a region of the screen to at least one other region of the screen.2. A device in accordance with claim 1, further comprising ananti-reflective treatment disposed on the conically shaped barrier.
 3. Adevice in accordance with claim 2, wherein the anti-reflective treatmentis selected from the group consisting of anti-reflective coatings,baffles, and optical felt.
 4. A device in accordance with claim 1,wherein the base of the barrier is coterminous with the bottom of thescreen.
 5. A device in accordance with claim 1, wherein the panoramicscreen includes a vertical axis of curvature that is parallel to avertical axis of the conically shaped barrier.
 6. A device in accordancewith claim 5, wherein the vertical axis of the conically shaped barrieris collinear with the vertical axis of the screen.
 7. A device inaccordance with claim 1, wherein the projector comprises multipleprojectors disposed near the projection point, configured to project acomposite image upon the screen.
 8. A device in accordance with claim 1,wherein the projector comprises: a) a linear array projector, configuredto project a vertical line of pixels at a refresh rate; and b) arotating scanning mirror, disposed substantially at the projectionpoint, configured to rotate about a vertical axis at one half therefresh rate of the linear array projector, and to reflect the verticalline of pixels onto the screen.
 9. A device in accordance with claim 8,wherein the projector further comprises a folding mirror, disposedbetween the linear array projector and the scanning mirror, configuredto reflect the vertical line of pixels onto the scanning mirror.
 10. Adevice in accordance with claim 8, wherein the panoramic screen includesa vertical axis of curvature that is parallel to a vertical axis of theconically shaped barrier and parallel to the vertical axis of thescanning mirror.
 11. A device in accordance with claim 1, wherein thescreen is a rear-projection screen
 12. A device in accordance with claim11, further comprising a curved mirror, configured to reflect apanoramic image from the screen to an offset viewing point.
 13. A devicein accordance with claim 1, wherein the screen is doubly curved.
 14. Adevice in accordance with claim 1, wherein the projector comprises: a) alinear array projector, configured to project a vertical line of pixelsat a refresh rate; and b) a rotating scanning mirror, disposedsubstantially at the projection point, configured to rotate about avertical axis at one half the refresh rate of the linear arrayprojector, and to reflect the vertical line of pixels onto the screen.15. A device in accordance with claim 1, wherein the curved projectionscreen defines an arc of greater than 180° and less than 360°, andfurther comprising a baffle, extending between a rearward edge of thescreen and the reflection barrier, configured to block reflectionsbetween rearward portions of the screen.
 16. A reflection barrier for apanoramic projection system, the system including a curved projectionscreen, having a center of curvature and a bottom, and a panoramicprojector, configured to project an image onto the projection screenfrom a projection point located substantially above the projectionscreen, the barrier comprising: a) a substantially conically shapedbarrier, having a base disposed toward the bottom of the projectionscreen, and an apex region disposed toward the projection point,configured to block reflections from a region of the screen to at leastone other region of the screen.
 17. A device in accordance with claim16, further comprising an anti-reflective treatment disposed on theconically shaped barrier.
 18. A device in accordance with claim 17,wherein the anti-reflective treatment is selected from the groupconsisting of anti-reflective coatings, baffles, and optical felt.
 19. Adevice in accordance with claim 16, wherein the projector comprisesmultiple projectors disposed near the projection point, configured toproject a composite image upon the screen.
 20. A device in accordancewith claim 16, wherein the base of the barrier is coterminous with thebottom of the screen.
 21. A device in accordance with claim 16, whereinthe panoramic screen includes a vertical axis of curvature that isparallel to a vertical axis of the conically shaped barrier.
 22. Adevice in accordance with claim 21, wherein the vertical axis of theconically shaped barrier is collinear with the vertical axis of thescreen.
 23. A device in accordance with claim 16, wherein the curvedprojection screen defines an arc of greater than 180° and less than360°, and further comprising a baffle, extending between a rearward edgeof the screen and the reflection barrier, configured to blockreflections between rearward portions of the screen.
 24. A panoramicdisplay system, comprising: a) a curved projection screen, having abottom and a center of curvature; b) a projection point, locatedsubstantially above the projection screen; c) a panoramic projector,configured to project an image onto the projection screen, the projectorincluding: i) a linear array projector configured to project a verticalline of pixels at a refresh rate; and ii) a rotating scanning mirror,disposed substantially at the projection point, configured to rotateabout a vertical axis at one half the refresh rate of the linear arrayprojector, and to reflect the vertical line of pixels onto the screen;and d) a substantially conically shaped barrier, having a base disposedtoward the bottom of the projection screen, an apex region disposedtoward the projection point, and a vertical axis that is substantiallycollinear with the center of curvature of the screen, the barrier beingconfigured to substantially block reflections from a region of thescreen to at least one other region of the screen.